Abstract

In this article the feasibility of gravity field determination with very high-low satellite-to-satellite tracking, as intended as part of the GETRIS (“Geodesy and Time Reference in Space”) mission concept, is investigated. For this purpose several geostationary satellites (GEOs) are positioned around the Earth. A microwave system is used to determine the relative position between satellites in low Earth orbits (LEOs) and GEOs with very high accuracy, from which the gravity field of the Earth can be estimated.This concept is simulated to retrieve the time-variable gravity field caused by temporal changes in continental hydrology. The simulation is based on simplified assumptions, taking only errors of the ranging instrument into account. The gravity field is recovered in a closed-loop environment from the simulated observations. Furthermore, the possibility of enhancing GRACE results with GEO-LEO tracking is investigated.Overall the results show that the GEO-LEO concept is very promising, since it possibly reduces some of the weaknesses of the LEO-LEO tracking concept and measures the radial component of the Earth’s gravity field. Due to the option of multi-satellite tracking, the time-variable gravity field might be observed within shorter time periods than with a single GRACE-like mission. However, more detailed simulations are required to draw final conclusions on the exact magnitude of benefit.